This invention relates to a system for guiding in which flying vehicles such as guided missiles are guided by a beam rider system, (hereinafter referred to as "light beam guide systems" when applicable).
A beam rider system using light wave for guiding a flying vehicle is superior to a passive system in which a guiding operation is performed by homing on infrared rays emitted from the target, and to an active or semiactive system in which a radio wave is emitted to the target from the flying vehicle itself or from a position different from the launcher's position, and the radio wave reflected by the target is detected by the flying vehicle to home on the target, in that as the light beam has a sharp directivity, the beam rider system using a light beam is scarcely interfered with by radio waves or light beams from the target.
However, since the beam rider system utilizes a light beam, it is necessary to increase the intensity of the light beam so as to distinguish the former from natural light, and furthermore it is required to apply a light beam having a certain diameter to a receiver of the flying vehicle.
These two requirements are contradictory to each other if the power of the light beam is maintained constant. More specifically, if the diameter of the beam is decreased to increase the intensity thereof, the size of the spot of the light beam formed on a receiver of the flying vehicle is decreased; however, the intensity of the light beam must be decreased if it is intended to increase the size of the spot of the light beam to a predetermined value. This is one of the drawbacks of the conventional beam rider system.
Furthermore, in the beam rider system, no matter where the flying vehicle is in a range predetermined from the center of the light beam, information on the displacement and its direction with respect to the center of the light beam must be obtained from signals received by the receiver of the flying vehicle. However, in order to obtain such information it is necessary to provide an intricate process, namely, modulation of a light beam. Especially in the case where the scanning is conducted with a light beam having these two pieces of information, it is required to increase the scanning speed for the response of the flying vehicle. If the scanning speed is increased, the receiving period of the scanning beam becomes too small for the transmission of the two pieces of information. This is a severe limitation on the beam rider system.